1. Field of the Invention
This invention relates to a lighting device, specifically to a lamp reflector used with gas discharge light sources. More particularly, the invention is directed to a reflector design intended to suppress radio frequency electro-magnetic radiation from a light source.
2. Description of the Prior Art
Heretofore, EMI (electro-magnetic interference) from a source of EMR (electro-magnetic radiation) has been suppressed by shielding that source. Opaque materials such as metals, metal filled plastics or metallic coatings are used for EMI shielding of electronic components, ballasts, etc.
Discharge light sources emitting in the visible spectral range, generate a certain amount of EMR due to the nature of the processes in the source and its excitation. The level of that EMR could cause serious interference with electronic devices. One example of such a source is a neon light tube.
Opaque shielding materials are not applicable, since they would not pass the visible radiation.
To provide EMI shielding for sources of this nature, woven metal wire meshes with small cell size are widely used. Disadvantages of this approach include increased cost and performance limitations. Regarding increased costs, the addition of the wire mesh increases both component and assembly cost, affecting the overall cost of the finished product.
Regarding performance limitations, the size of the mesh cells applies limitation on the high frequency range that can be efficiently shielded, and reduces the light output due to absorption and scattering from the mesh.
Another technique of EMI shielding is the use of conductive coatings that are transparent in the visible range. ITO (Indium Tin Oxide) is widely used. Although this technique does not have the performance limitations mentioned above, the application of the coating is expensive, and the coating itself is highly toxic.